In a 17‑year‑old girl with severe posterior neck pain radiating to the shoulders, a cervical X‑ray shows mild loss of cervical lordosis due to muscle spasm, and labs are negative antinuclear antibody and rheumatoid factor <10 IU/mL, what is the most likely diagnosis or impression?

Most Likely Diagnosis: Mechanical Neck Pain with Muscle Spasm

The most likely impression is benign mechanical neck pain with protective muscle spasm causing loss of cervical lordosis—a common radiographic finding in young patients with neck pain that does not indicate serious pathology. The negative inflammatory markers (ANA and RF) effectively rule out autoimmune/rheumatic causes, and the X-ray findings are consistent with a functional, reversible condition rather than structural disease.

Clinical Reasoning

Why This is Benign Mechanical Pain

The clinical picture strongly suggests non-specific mechanical neck pain:

• Age and demographics: A 17-year-old girl falls into the demographic where mechanical neck pain is extremely common, with an estimated 1-year prevalence of 25% in the general population 1
• Negative inflammatory workup: ANA negative and RF <10 IU/mL essentially exclude systemic lupus erythematosus, Sjögren syndrome, and rheumatoid arthritis 2, 3
• Radiographic findings: Loss of cervical lordosis attributed to muscle spasm is a frequently reported finding but lacks strong evidence as a pathological indicator

Critical Evidence About "Loss of Lordosis"

The interpretation that loss of cervical lordosis equals muscle spasm is not well-supported by evidence:

• Research demonstrates that 19-42% of normal, asymptomatic individuals have straight cervical spines on X-ray 4
• A 2013 study found no significant difference in cervical alignment between patients with neck injury and those without (p > 0.100), concluding that alterations in cervical lordosis "should not be associated with muscle spasm caused by neck pain" 5
• A 2025 study of 255 neck pain patients found no association between degree of lordosis and pain severity or radiation pattern (p=0.969) 6
• Women are more likely than men to have straight cervical spines (odds ratio 2.81), suggesting anatomical variation rather than pathology 4

Therefore, the X-ray finding is likely a normal variant or positioning artifact rather than a pathological sign.

Differential Considerations

What Has Been Ruled Out

The negative serological workup is particularly valuable:

• Rheumatoid arthritis: RF <10 is negative; while ANA can be positive in RA, the combination of negative RF and clinical picture makes this unlikely 7, 3
• Systemic lupus erythematosus: Negative ANA has high negative predictive value
• Sjögren syndrome: Would typically show positive ANA (especially anti-SSA/Ro), which can be positive even with negative ANA-IIF in some cases, but clinical context doesn't suggest this 2

Possible Cervical Radiculopathy

The radiation to shoulders raises the question of radiculopathy:

• Cervical radiculopathy has an annual incidence of 83 per 100,000 and commonly presents with neck and upper limb pain 1
• However, plain X-rays are inadequate for diagnosing radiculopathy—they cannot visualize disc herniations or nerve root compression 1
• 75-90% of cervical radiculopathy cases resolve with conservative therapy 1

Recommended Management Approach

Immediate Clinical Assessment

Look for "red flag" symptoms that would warrant advanced imaging:

• Constitutional symptoms (fever, unexplained weight loss)
• Progressive neurological deficits (weakness, numbness in specific dermatomal distribution)
• Bowel/bladder dysfunction
• Night pain or pain at rest
• History of malignancy
• Immunosuppression or IV drug use
• Elevated inflammatory markers (ESR, CRP, WBC) 1

If No Red Flags Present

Conservative management is appropriate:

• The X-ray has already been performed and shows no structural abnormality
• No additional imaging is indicated at this time 1
• Conservative therapy including physical therapy, NSAIDs, and activity modification
• Reassess in 4-6 weeks

If True Radiculopathy is Suspected

Clinical examination should assess for:

• Dermatomal sensory changes
• Myotomal weakness
• Reflex asymmetry
• Positive Spurling's test (though physical examination has limited accuracy for cervical radiculopathy) 1

If radiculopathy is confirmed clinically and symptoms persist beyond 6 weeks:

• MRI cervical spine without contrast is the imaging modality of choice 1
• MRI must be interpreted in clinical context due to high false-positive rates in asymptomatic individuals 1
• CT is inferior to MRI for evaluating disc herniations and nerve root compression 1

Common Pitfalls to Avoid

1. Over-interpreting loss of lordosis: This finding is common in normal individuals and does not reliably indicate muscle spasm or pathology 4, 8, 5

2. Ordering MRI too early: In the absence of red flags or true radiculopathy, MRI is not indicated and will likely show age-related changes that are clinically irrelevant 1

3. Assuming radiation to shoulders equals radiculopathy: Mechanical neck pain commonly refers to the shoulder region without nerve root involvement 9

4. Missing red flags: While this case appears benign, always systematically assess for concerning features that would change management 1

Clinical Bottom Line

This 17-year-old has benign mechanical neck pain with a normal variant X-ray finding. The negative inflammatory markers exclude autoimmune disease. Conservative management with clinical reassessment is appropriate. Advanced imaging is only warranted if red flag symptoms develop or if true radiculopathy persists beyond 6 weeks of conservative therapy.